Add missing coma

Author: layus

autoload/vundle/installer.vim

@@ -374,7 +374,7 @@ func! s:make_git_command(bundle, args) abort
 
   let git = ['git', '--git-dir='.gitdir, '--work-tree='.workdir]
 
-  return join(map(git + a:args 'vundle#installer#shellesc'))
+  return join(map(git + a:args, 'vundle#installer#shellesc'))
 endf
 
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